A method is provided for stabilizing an electro-optic substrate employed in a waveguide device. The terminal sends a signature waveform based on the uplink access configuration information, prior to receiving system information in addition to the first system information, whereby the signature waveform enables the base station to transition from a relatively low power operating mode to a relatively high power operating mode. The IMD is fitted into an esophageal catheter lumen with the fixation mechanism aimed toward the catheter distal end opening whereby the bend in the flexible member is straightened. The device comprises a rod sliding in the shaft and passing through the hole of the inner face of the bottom of the receptacle, said rod being provided with a spring maintaining an end of the rod lifted inside the receptacle in contact with the capsule, the other end being inside the shaft.